The wikipedia article on the PMI says
When we develop a new theory, the central ideas of the old one usually become refuted. Parts of the old theory, however, we carry over to the new one
This seems to be at least part of the reason we have alternatives to "naive realism".
But there's no agreement on what parts of our current theories are knowledge and should be retained.
Can't philosophers identify a commonality between what actually has been retained through past theory change? And if there is no commonality, what then?